1. Field of the Invention
This invention relates to a catalyst system, a process for making the catalyst system and a process for olefin polymerization using the catalyst system. More specifically, this invention relates to a catalyst system using a diethylaluminum alkoxide, such as diethylaluminum ethoxide, with an aluminum alkyl, such as triethylaluminum, as a cocatalyst, to a process for making the catalyst system and to a polymerization of olefins, specifically propylene, using the catalyst system which increases polymerization yield.
2. Description of the Prior Art
Diethylaluminum ethoxide (DEAl-E) is known as a co-catalyst. U.S. Pat. No. 4,335,016 discloses a new catalyst activated with a cocatalyst of an organometallic compound or hydrogen or mixtures thereof, such as alkyl lithium, alkyl magnesium, alkyl aluminum, alkyl aluminum halide or alkyl zinc. Diethylaluminum ethoxide is listed as an example of a cocatalyst but the working examples of the patent used triisobutylaluminum as the cocatalyst. There is no disclosure that a mixture of DEAl-E with any other cocatalyst would result in an increase in polymerization yield.
U.S. Pat. No. 4,985,515 discloses a combination of triethyl aluminum (TEAl) and diethylaluminum ethoxide (DEAl-E) as a co-catalyst for catalyst for the polymerization of olefins. Several other combinations of organoaluminum compounds as co-catalysts are also disclosed without showing any superior results of one combination over the others.
U.S. Pat. No. 4,399,055 discloses a combination of triethylaluminum, diethylaluminum ethoxide and diethylaluminum chloride (DEAC). Other combinations are also disclosed including triethylaluminum and diethylaluminum ethoxide but no comparison of the effect of using different combinations of co-catalyst on polymerization yield is reported. The working examples reported use the TEAl/DEAl-E/DEAC combination.
The patents above and others of the prior are concerned with the ratio of co-catalyst to Ziegler-Natta type catalyst component rather than a mixture of co-catalysts which affects polymerization yield. It would be advantageous to provide a mixture of co-catalysts which would improve polymerization yield.